This invention relates to automatic shutoff valves in residential combined ancillary or domestic and fire sprinkler piping systems.
Residential domestic shutoff valves are used in dual-purpose residential water supply piping systems serving both the domestic and residential fire protection sprinkler system needs under NFPA (xe2x80x9cNational Fire Protection Associationxe2x80x9d) 13D or NFPA 13R, the complete disclosures of which are incorporated herein by reference. When an automatic fire sprinkler operates, the residential domestic shutoff valve automatically shuts off water flow to the domestic system and diverts the available water supply to the fire sprinkler system. Consequently, when the residential domestic shutoff valve is utilized, the system designer need not add the domestic flow demand to the fire sprinkler system flow demand, as would otherwise be required by NFPA 13D or NFPA 13R.
Use of a residential domestic shutoff valve may be considered when the water supply cannot adequately provide for both the domestic design demand and fire sprinkler flow demand, or when it is desirable to increase the effectiveness of the fire sprinkler system by automatically shutting off domestic flow. A typical domestic water supply shutoff valve for use with a fire protection system water supply piping is described in Martin et al. U.S. Pat. No. 5,236,002, also owned by the present assignee.
According to the invention, an automatic water supply shutoff valve for use in connection with fire protection water supply piping system comprises a valve body defining a cavity in communication among a supply inlet for connection to a supply of water, a first, ancillary outlet for connection to ancillary supply piping, and a second, fire protection outlet for connection to fire protection piping; and a piston disposed within the cavity and defining a piston passageway, the piston being mounted for movement between a first position with the piston passageway connecting the supply inlet with the first, ancillary outlet, for flow of water therebetween, and a second position with the piston passageway connecting the supply inlet with the second, fire protection outlet, for flow of water therebetween, movement of the piston between the first position and the second position being responsive to biasing forces acting against the piston, the biasing forces comprising a first biasing force from the supply inlet acting over a first surface area of the piston, a second biasing force from the fire protection outlet acting over a second surface area of the piston, and a third biasing force acting against the piston, the first biasing force, urging the piston toward its second position, being opposed by a combination of the second biasing force and the third biasing force, together urging the piston toward its first position, the piston defining a piston inlet in communication between the supply inlet and the piston passageway and a plurality of radial piston outlets in the first position in communication between the piston passageway and the first, ancillary outlet and in the second position in communication between the piston passageway and the second, fire protection outlet.
Preferred embodiments of the invention may include one or more of the following additional features. The third biasing force comprises gravity, and/or the valve comprises a compression spring engaged between the piston and the body, and the third biasing force comprises a spring force applied against the piston by the compression spring. The valve further comprises means for restricting flow between the first, ancillary outlet and the second, fire protection outlet. The first surface area of the piston and the second surface area of the piston are substantially equal. Preferably the piston has a cylindrical shape and the first surface area and/or the second surface area of the piston is equal to or greater than a cross-sectional area of the piston taken on a plane perpendicular to the axis of the piston. The first direction of movement of the piston and the second direction of movement of the piston are opposite directions along a cylindrical axis of the piston. An interconnecting passageway between the first, ancillary outlet and the second, fire protection outlet is defined between an outer surface of the piston and an opposed inner surface of the valve body. Flow of water through the interconnecting passageway is restricted by at least a minimum clearance between the outer surface of the piston and the opposed inner surface of the valve body, the minimum surface being relatively small compared to the areas of the first, ancillary outlet and the second, fire protection outlet. The minimum clearance extends along the axis of the piston in a region of a fixed distance equal to or greater than the axial length of the radial piston outlets. The piston is disposed for movement to an intermediate position, between the first position and the second position, for resisting flow from the supply inlet toward the first, ancillary outlet and for resisting flow from the supply inlet toward the second, fire protection outlet, and, the minimum clearance, with the piston in the intermediate position and the radial piston outlets positioned within the region of fixed distance, resists flow from the radial piston outlets toward the first, ancillary outlet and toward the second, fire protection outlet. Preferably, flow of water through the interconnecting passageway is restricted by a first annular seal, and, more preferably, by first and second annular seals, engaged between the outer surface of the piston and the opposed inner surface of the valve body. The first and second annular seals are spaced apart along the axis of the piston and defining a region of fixed distance equal to or greater than the axial length of the radial piston outlets. The piston is disposed for movement to an intermediate position, between the first position and the second position, for resisting flow from the supply inlet toward the first, ancillary outlet and for resisting flow from the supply inlet toward the second, fire protection outlet, and the first annular seal and the second annular seal cooperate, with the piston in the intermediate position and the radial piston outlets positioned between the first annular seal and the second annular seal and within the region of fixed distance, to resist flow from the radial piston outlets toward the first, ancillary outlet and toward the second, fire protection outlet. The annular seals comprise u-shape seals. The fire protection outlet is connected to a fire protection sprinkler piping system with one or more fire protection sprinklers, the fire sprinkler fire protection piping system having a standby (static) condition closed to flow from fire protection outlet and an active condition open to flow from the fire protection outlet, the active condition providing a flow from the fire protection outlet. Preferably, the piston is responsive to change of the fire protection sprinkler piping system from the static condition to the active condition to move from the first position toward the second position, e.g., reduced pressure in the fire sprinkler piping system resulting from a single sprinkler flow reduces the second biasing force allowing the piston to move toward the second position. The piston returns to the first position when the fire protection sprinkler piping system returns to the static condition. The piston and the body, in the first position of the piston, together define a first generally circumferential ancillary flow passageway in communication between the plurality of radial piston outlets and the ancillary outlet, and the piston and the body, in the second position of the piston, together define a second generally circumferential fire protection flow passageway in communication between the plurality of radial piston outlets and the fire protection outlet. The piston moves from the first position toward the second position in response to a differential of pressure between the supply inlet and the fire protection outlet of approximately 2 psi minus the weight of the piston.
Advantages of the residential domestic automatic shutoff valve of the invention include a built-in check valve in the fire protection outlet that eliminates the need for a separate check valve. Also, the residential domestic automatic shutoff valve of the invention automatically resets, thereby eliminating the need for valve disassembly after a fire protection sprinkler piping system test or operation. The residential domestic shutoff valve of the invention maximizes the effective use of an existing water supply and therefore, in areas with limited water supplies, it may eliminate the necessity of adding costly pumps, pressurized reservoirs, or electrically operated domestic shutoff valves.
The details of one or more embodiments of the invention are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the invention will be apparent from the description and drawings, and from the claims.